今日看点：bot短期密集访问形成的流量高峰有哪些？如何解决？

周末大清早收到封警报邮件，估计网站被攻击了，要么就是缓存日志memory的问题。打开access.log 看了一眼，原来该时间段内大波的bot（bot： 网上机器人；自动程序 a computer programthat performs a particular task again and again many times）访问了我的网站。

http://ltx71.com  http://mj12bot.com http://www.bing.com/bingbot.htm http://ahrefs.com/robot/ http://yandex.com/bots

(资料图)

website.com (AWS) - Monitor is Down

Down since Mar 25, 2017 1:38:58 AM CET

Site Monitored

Resolved IP

54.171.32.xx

Reason

Service Unavailable.

Monitor Group

XX Applications

Outage Details

LocationResolved IPReasonLondon - UK (5.77.35.xx)54.171.32.xxService Unavailable.Headers : HTTP/1.1 503 Service Unavailable: Back-end server is at capacity Content-Length : 0 Connection : keep-alive GET / HTTP/1.1 Cache-Control : no-cache Accept : */* Connection : Keep-Alive Accept-Encoding : gzip User-Agent : Site24x7 Host : xxxSeattle - US (104.140.20.xx)54.171.32.xxService Unavailable.Headers : HTTP/1.1 503 Service Unavailable: Back-end server is at capacity Content-Length : 0 Connection : keep-alive GET / HTTP/1.1 Cache-Control : no-cache Accept : */* Connection : Keep-Alive Accept-Encoding : gzip User-Agent : Site24x7 Host : xxx

上网搜了一下，发现许多webmaster都遇到了由于bot短期密集访问形成的流量高峰而无法其它终端提供服务的问题。从这篇文章的分析中，我们看到有这样几种方法来block这些web bot。

1.      robots.txt

许多网络爬虫都是先去搜索robots.txt，如下所示：

"199.58.86.206" - - [25/Mar/2017:01:26:50 +0000] "GET /robots.txt HTTP/1.1" 404 341 "-" "Mozilla/5.0 (compatible; MJ12bot/v1.4.8; http://mj12bot.com/)" "199.58.86.206" - - [25/Mar/2017:01:26:54 +0000] "GET / HTTP/1.1" 200 129989 "-" "Mozilla/5.0 (compatible; MJ12bot/v1.4.8; http://mj12bot.com/)" "162.210.196.98" - - [25/Mar/2017:01:39:18 +0000] "GET /robots.txt HTTP/1.1" 404 341 "-" "Mozilla/5.0 (compatible; MJ12bot/v1.4.8; http://mj12bot.com/)"

许多bot的发布者也谈到了如果不希望被爬取，应该如何来操作，就以MJ12bot为例：

How can I block MJ12bot?

MJ12bot adheres to the robots.txtstandard. If you want the bot to prevent website from being crawled then add the following text to your robots.txt:

User-agent: MJ12bot

Disallow: /

Please do not waste your time trying to block bot via IP in htaccess - we do not use any consecutive IP blocks so your efforts will be in vain. Also please make sure the bot can actually retrieve robots.txt itself - if it can"t then it will assume (this is the industry practice) that its okay to crawl your site.

If you have reason to believe that MJ12bot did NOT obey your robots.txt commands, then please let us know via email: bot@majestic12.co.uk. Please provide URL to your website and log entries showing bot trying to retrieve pages that it was not supposed to.

How can I slow down MJ12bot?

You can easily slow down bot by adding the following to your robots.txt file:

User-Agent: MJ12bot

Crawl-Delay:   5

Crawl-Delay should be an integer number and it signifies number of seconds of wait between requests. MJ12bot will make an up to 20 seconds delay between requests to your site - note however that while it is unlikely, it is still possible your site may have been crawled from multiple MJ12bots at the same time. Making high Crawl-Delay should minimise impact on your site. This Crawl-Delay parameter will also be active if it was used for * wildcard.

If our bot detects that you used Crawl-Delay for any other bot then it will automatically crawl slower even though MJ12bot specifically was not asked to do so.

那么我们可以写如下的

User-agent: YisouSpider

Disallow: /

User-agent: EasouSpider

Disallow: /

User-agent: EtaoSpider

Disallow: /

User-agent: MJ12bot

Disallow: /

另外，鉴于很多bot都会去访问这些目录：

/wp-login.php /wp-admin/

/trackback/

/?replytocom=

…

许多WordPress网站也确实用到了这些文件夹，那么如何在不影响功能的情况下做一些调整呢？

robots.txt修改之前robots.txt修改之后

User-agent: *

Disallow: /wp-admin

Disallow: /wp-content/plugins

Disallow: /wp-content/themes

Disallow: /wp-includes

Disallow: /?s=User-agent: *

Disallow: /wp-admin

Disallow: /wp-*

Allow: /wp-content/uploads/

Disallow: /wp-content

Disallow: /wp-login.php

Disallow: /comments

Disallow: /wp-includes

Disallow: /*/trackback

Disallow: /*?replytocom*

Disallow: /?p=*&preview=true

Disallow: /?s=

不过，也可以看到许多爬虫并不理会robots.txt，以这个为例，就没有先去访问robots.txt

"10.70.8.30, 163.172.65.40" - - [25/Mar/2017:02:13:36 +0000] "GET / HTTP/1.1" 200 129989 "-" "Mozilla/5.0 (compatible; AhrefsBot/5.2; +http://ahrefs.com/robot/)" "178.63.23.67, 163.172.65.40" - - [25/Mar/2017:02:13:42 +0000] "GET / HTTP/1.1" 200 129989 "-" "Mozilla/5.0 (compatible; AhrefsBot/5.2; +http://ahrefs.com/robot/)" "178.63.23.67, 163.172.65.40" - - [25/Mar/2017:02:14:17 +0000] "GET /static/js/utils.js HTTP/1.1" 200 5345 "http://iatatravelcentre.com/" "Mozilla/5.0 (compatible; AhrefsBot/5.2; +http://ahrefs.com/robot/)" "178.63.23.67, 163.172.65.40" - - [25/Mar/2017:02:14:17 +0000] "GET /static/css/home.css HTTP/1.1" 200 8511 "http://iatatravelcentre.com/" "Mozilla/5.0 (compatible; AhrefsBot/5.2; +http://ahrefs.com/robot/)"

这个时候就要试一下其他几种方法。

2.      .htaccess

原理就是利用URL rewrite，只要发现访问来自于这些agent，就禁止其访问。作者“~吉尔伽美什”的这篇文章介绍了关于.htaccess的很多用法。

5. Blocking users by IP 根据IP阻止用户访问order allow,deny  deny from 123.45.6.7  deny from 12.34.5. (整个C类地址)  allow from all  6. Blocking users/sites by referrer 根据referrer阻止用户/站点访问需要mod_rewrite模块  例1. 阻止单一referrer: badsite.comRewriteEngine on  # Options +FollowSymlinks  RewriteCond %{HTTP_REFERER} badsite\.com [NC]  RewriteRule .* - [F]  例2. 阻止多个referrer: badsite1.com, badsite2.comRewriteEngine on  # Options +FollowSymlinks  RewriteCond %{HTTP_REFERER} badsite1\.com [NC,OR]  RewriteCond %{HTTP_REFERER} badsite2\.com  RewriteRule .* - [F]  [NC] - 大小写不敏感(Case-insensite)  [F] - 403 Forbidden  注意以上代码注释掉了”Options +FollowSymlinks”这个语句。如果服务器未在 httpd.conf 的 段落设置 FollowSymLinks, 则需要加上这句，否则会得到”500 Internal Server error”错误。  7. Blocking bad bots and site rippers (aka offline browsers) 阻止坏爬虫和离线浏览器需要mod_rewrite模块  坏爬虫? 比如一些抓垃圾email地址的爬虫和不遵守robots.txt的爬虫(如baidu?)  可以根据 HTTP_USER_AGENT 来判断它们  (但是还有更无耻的如”中搜 zhongsou.com”之流把自己的agent设置为 “Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 5.0)” 太流氓了，就无能为力了)  RewriteEngine On  RewriteCond %{HTTP_USER_AGENT} ^BlackWidow [OR]  RewriteCond %{HTTP_USER_AGENT} ^Bot\ mailto:craftbot@yahoo.com [OR]  RewriteCond %{HTTP_USER_AGENT} ^ChinaClaw [OR]  RewriteCond %{HTTP_USER_AGENT} ^Custo [OR]  RewriteCond %{HTTP_USER_AGENT} ^DISCo [OR]  RewriteCond %{HTTP_USER_AGENT} ^Download\ Demon [OR]  RewriteCond %{HTTP_USER_AGENT} ^eCatch [OR]  RewriteCond %{HTTP_USER_AGENT} ^EirGrabber [OR]  RewriteCond %{HTTP_USER_AGENT} ^EmailSiphon [OR]  RewriteCond %{HTTP_USER_AGENT} ^EmailWolf [OR]  RewriteCond %{HTTP_USER_AGENT} ^Express\ WebPictures [OR]  RewriteCond %{HTTP_USER_AGENT} ^ExtractorPro [OR]  RewriteCond %{HTTP_USER_AGENT} ^EyeNetIE [OR]  RewriteCond %{HTTP_USER_AGENT} ^FlashGet [OR]  RewriteCond %{HTTP_USER_AGENT} ^GetRight [OR]  RewriteCond %{HTTP_USER_AGENT} ^GetWeb! [OR]  RewriteCond %{HTTP_USER_AGENT} ^Go!Zilla [OR]  RewriteCond %{HTTP_USER_AGENT} ^Go-Ahead-Got-It [OR]  RewriteCond %{HTTP_USER_AGENT} ^GrabNet [OR]  RewriteCond %{HTTP_USER_AGENT} ^Grafula [OR]  RewriteCond %{HTTP_USER_AGENT} ^HMView [OR]  RewriteCond %{HTTP_USER_AGENT} HTTrack [NC,OR]  RewriteCond %{HTTP_USER_AGENT} ^Image\ Stripper [OR]  RewriteCond %{HTTP_USER_AGENT} ^Image\ Sucker [OR]  RewriteCond %{HTTP_USER_AGENT} Indy\ Library [NC,OR]  RewriteCond %{HTTP_USER_AGENT} ^InterGET [OR]  RewriteCond %{HTTP_USER_AGENT} ^Internet\ Ninja [OR]  RewriteCond %{HTTP_USER_AGENT} ^JetCar [OR]  RewriteCond %{HTTP_USER_AGENT} ^JOC\ Web\ Spider [OR]  RewriteCond %{HTTP_USER_AGENT} ^larbin [OR]  RewriteCond %{HTTP_USER_AGENT} ^LeechFTP [OR]  RewriteCond %{HTTP_USER_AGENT} ^Mass\ Downloader [OR]  RewriteCond %{HTTP_USER_AGENT} ^MIDown\ tool [OR]  RewriteCond %{HTTP_USER_AGENT} ^Mister\ PiX [OR]  RewriteCond %{HTTP_USER_AGENT} ^Navroad [OR]  RewriteCond %{HTTP_USER_AGENT} ^NearSite [OR]  RewriteCond %{HTTP_USER_AGENT} ^NetAnts [OR]  RewriteCond %{HTTP_USER_AGENT} ^NetSpider [OR]  RewriteCond %{HTTP_USER_AGENT} ^Net\ Vampire [OR]  RewriteCond %{HTTP_USER_AGENT} ^NetZIP [OR]  RewriteCond %{HTTP_USER_AGENT} ^Octopus [OR]  RewriteCond %{HTTP_USER_AGENT} ^Offline\ Explorer [OR]  RewriteCond %{HTTP_USER_AGENT} ^Offline\ Navigator [OR]  RewriteCond %{HTTP_USER_AGENT} ^PageGrabber [OR]  RewriteCond %{HTTP_USER_AGENT} ^Papa\ Foto [OR]  RewriteCond %{HTTP_USER_AGENT} ^pavuk [OR]  RewriteCond %{HTTP_USER_AGENT} ^pcBrowser [OR]  RewriteCond %{HTTP_USER_AGENT} ^RealDownload [OR]  RewriteCond %{HTTP_USER_AGENT} ^ReGet [OR]  RewriteCond %{HTTP_USER_AGENT} ^SiteSnagger [OR]  RewriteCond %{HTTP_USER_AGENT} ^SmartDownload [OR]  RewriteCond %{HTTP_USER_AGENT} ^SuperBot [OR]  RewriteCond %{HTTP_USER_AGENT} ^SuperHTTP [OR]  RewriteCond %{HTTP_USER_AGENT} ^Surfbot [OR]  RewriteCond %{HTTP_USER_AGENT} ^tAkeOut [OR]  RewriteCond %{HTTP_USER_AGENT} ^Teleport\ Pro [OR]  RewriteCond %{HTTP_USER_AGENT} ^VoidEYE [OR]  RewriteCond %{HTTP_USER_AGENT} ^Web\ Image\ Collector [OR]  RewriteCond %{HTTP_USER_AGENT} ^Web\ Sucker [OR]  RewriteCond %{HTTP_USER_AGENT} ^WebAuto [OR]  RewriteCond %{HTTP_USER_AGENT} ^WebCopier [OR]  RewriteCond %{HTTP_USER_AGENT} ^WebFetch [OR]  RewriteCond %{HTTP_USER_AGENT} ^WebGo\ IS [OR]  RewriteCond %{HTTP_USER_AGENT} ^WebLeacher [OR]  RewriteCond %{HTTP_USER_AGENT} ^WebReaper [OR]  RewriteCond %{HTTP_USER_AGENT} ^WebSauger [OR]  RewriteCond %{HTTP_USER_AGENT} ^Website\ eXtractor [OR]  RewriteCond %{HTTP_USER_AGENT} ^Website\ Quester [OR]  RewriteCond %{HTTP_USER_AGENT} ^WebStripper [OR]  RewriteCond %{HTTP_USER_AGENT} ^WebWhacker [OR]  RewriteCond %{HTTP_USER_AGENT} ^WebZIP [OR]  RewriteCond %{HTTP_USER_AGENT} ^Wget [OR]  RewriteCond %{HTTP_USER_AGENT} ^Widow [OR]  RewriteCond %{HTTP_USER_AGENT} ^WWWOFFLE [OR]  RewriteCond %{HTTP_USER_AGENT} ^Xaldon\ WebSpider [OR]  RewriteCond %{HTTP_USER_AGENT} ^Zeus  RewriteRule ^.* - [F,L]  [F] - 403 Forbidden  [L] - 连接(Link) 8. Change your default directory page 改变缺省目录页面 DirectoryIndex index.html index.php index.cgi index.pl  9. Redirects 转向单个文件Redirect /old_dir/old_file.html http://yoursite.com/new_dir/new_file.html  整个目录Redirect /old_dir http://yoursite.com/new_dir  效果: 如同将目录移动位置一样  http://yoursite.com/old_dir -> http://yoursite.com/new_dir  http://yoursite.com/old_dir/dir1/test.html -> http://yoursite.com/new_dir/dir1/test.html  Tip: 使用用户目录时Redirect不能转向的解决方法当你使用Apache默认的用户目录，如 http://mysite.com/~windix，当你想转向 http://mysite.com/~windix/jump时，你会发现下面这个Redirect不工作:  Redirect /jump http://www.google.com  正确的方法是改成  Redirect /~windix/jump http://www.google.com  (source: .htaccess Redirect in “Sites” not redirecting: why?  )  10. Prevent viewing of .htaccess file 防止.htaccess文件被查看  order allow,deny  deny from all

3.      拒绝IP的访问

可以在Apache配置文件httpd.conf指明拒绝来自某些IP的访问。

Order allow,deny

Allow from all

Deny from5.9.26.210

Deny from162.243.213.131

但是由于很多时候，这些访问的IP并不固定，所以这种方法不太方便，而且修改了httpd.conf还要重启apache才能生效，所以建议采用修改.htaccess。